1-Methylbenzothiazolinospiro-2,3'-(2-methyl[3H]phenanthr[9,10-b][1,4]oxazine) and 1-Methylbenzothiazolinospiro-2,3'-(2'-methyl[3H]naphth[2,1-b][1,4]oxazine)

The single-crystal X-ray structures of two thiazolinospiro derivatives, C₂₄H₁₈N₂OS and C₂₀H₁₆N₂OS, suggest that their lack of photochromic behavior is due to electron-pair delocalization which reduces potential stabilization of a cationic intermediate.

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